Islamist forces say they have seized control of another town in southern Somalia, fueling fears of a direct assault on the country's weak interim government.

Officials with the Islamic courts say their militia entered the town of Sakow late Wednesday and took it over without encountering any resistance.

The takeover comes as the Somali government in Baidoa prepares for a possible attack by Islamist militias. Witnesses say government forces, allegedly backed by Ethiopian troops, have been digging trenches outside the town.

The United States Thursday urged both Ethiopia and Eritrea not to aggravate tensions in Somalia.

Islamic court leaders have declared a holy war against Ethiopia for allegedly sending its soldiers to assist the interim government. Ethiopia says it has only sent military instructors to train the army.

Eritrea has been accused of supporting the Islamists, a charge it denies.

Meanwhile Thursday, the government's deputy defense minister, Salad Ali Jelle, accused Islamists of kidnapping three Somali lawmakers who were driving to Baidoa from the capital, Mogadishu. There was no immediate comment from the Islamists.

The government and Islamists are slated to hold peace talks in the Sudanese capital of Khartoum on Monday.